Colt Defense LE6920CK: The Colt Conversion Kit contains the complete upper receiver group, including a charging handle, bolt carrier group, and back up sight. Conversion Kits are available in both the standard upper receiver with handguard configuration and Monolithic 1-piece upper receiver with free-floating barrel configuration. All barrels feature a 1/7 right hand twist. Now you can convert any Colt rifle to the most state of the art configurations.